I need ELISA/EIA kit to detect triiodothyronin (T3) level and the other one for thyroxin (T4) level of mouse and rat. It is easy to get ones for human, but so far I found difficulties to found the ones for mouse and rat. Hopefully I would get clue from you here.

Is rat or mouse T3 or T4 iodinated at different points or something? T3 and T4 are not proteins so, unless there is something chemically unique about them, I would think an assay for the human hormones would work just as well in rodents--all other things being equal, like, for example, there's no kind of rodent interfering molecule that scarfs up the human Elisa reagent, or some wierd thing like that.

But from the package insert of regular insulin kit I got, it is said that the kit will result 0 % cross link with rat and mouse insulin? It seems to me that the kit doesn't work for rodents' insulin. Or it means something else? I'm sorry my English is limit.

Yes, but insulin is a protein and the sequences of rat, human, and mouse insulin are different and may not be (apparently aren't) recognized by the Eliza antibodies. T3 and T4 are iodinated steroid-like molecules, not peptides or protein. There shouldn't be any difference in their structures from animal to animal--unless the points at which the iodine atoms are attached differs between species. I wouldn't think so, but I don't know that for a fact.